A typical packaging plastic bag has two face panels formed from a plastic film and juxtaposed with each other, a gusset extending from an upper end of the bag across at least part of the bag side and connecting the juxtaposed face panels at that location, and a slide fastener extending transversely at the upper end and comprising a slider, two profile strips that can be locked to each other and that are gripped by the slider, and two attachment flaps connected thereto and securing the slide fastener to the bag film inside the bag, movement of the slider limited by a first end of the slide fastener along the profile strips in a first direction connecting and movement limited by the second end of the slide fastener in a second direction separating the profile strips, whereby the gusset forms a spout with an opened slide fastener in the extended position, and the gusset is covered by the connected profile strips at the top at its upper end forming the spout in a closed position of the slide fastener, and, if the gusset is folded-in or if the slide fastener extends at the first end beyond the face panels and is arranged on the gusset forming the spout, this spout is fixed in a open position by the slide fastener.
A bag having the features described is known from EP 1 442 992 [U.S. Pat. No. 7,144,159]. According to the known embodiment the attachment flaps of the slide fastener are attached to inner faces of the bag by welding. The slide fastener may therefore also be attached without any problems by welding to bags having an outside layer, such as from polyester, that is not weldable or that is difficult to weld. Furthermore, the appearance of the bag is not adversely affected by the arrangement of the slide fastener. The known bag is a side-gusset bag having two gussets opposite each other and connecting the face panels, the gussets extending the entire height of the bag. The slide fastener extends across the entire width of the face panels, and is therefore also connected to the two gussets. The slide fastener projects over the upper edge of the bag film at its profile strips that can lock into each other such that the one spout-forming gusset is overlapped, e.g. closed by the locked together profile strips in the folded-in position and with the slide fastener closed.
While one of the attachment flaps extends completely along one of the face panels, the other attachment flap is attached both on the opposite face panel and to the inextensible gusset. The transition present between these areas forms a step, which is at high risk of leakage due to the overlapping layers and particularly due to the transition from two layers, e.g. the two face panels, to four layers, e.g. the two face panels with the gusset enfolded therein. Furthermore, unevenness may occur in the face panels at the transition such that the appearance of the bag is adversely affected.